Endoscopic Endonasal Transpterygoid Approach: Technical Lessons.

INDICATIONS CORRIDOR AND LIMITS OF EXPOSURE: The endoscopic endonasal transpterygoid approach (EETPA) provides direct access to the petrous apex, lateral clivus, inferior cavernous sinus compartment, jugular foramen, and infratemporal fossa. 1,2 In the coronal plane, it provides exposure far beyond a traditional sphenoidotomy. ANATOMIC ESSENTIALS NEED FOR PREOPERATIVE PLANNING AND ASSESSMENT: The pterygoid process of the sphenoid bone forms the junction between the body and greater sphenoid wing before bifurcating because it descends into medial and lateral plates. The key to this exposure lies in the region's bony foramina: the palatovaginal canal, vidian canal, and foramen rotundum. 3. ESSENTIALS STEPS OF THE PROCEDURE: After performing a maxillary antrostomy, stepwise exposure of these foramina leads to the pterygopalatine fossa. The sphenopalatine artery is cauterized as it becomes the posterior septal artery at the sphenopalatine foramen, and the maxillary sinus' posterior wall is opened to expose the pterygopalatine fossa. After mobilizing and retracting the contents of the pterygopalatine fossa, the pterygoid process is removed, improving access in the coronal plane. 4. PITFALLS/AVOIDANCE OF COMPLICATIONS: Vidian neurectomy causes decreased or absent lacrimation. Injury to the maxillary nerve or its branches results in facial, palatal, or odontogenic anesthesia or neuralgia. In addition, the EEPTA precludes the ability to raise an ipsilateral nasal septal flap, making it crucial to plan reconstruction preoperatively. 4,5. VARIANTS AND INDICATIONS FOR THEIR USE: There are 5 variants of the EEPTA: extended pterygopalatine fossa, lateral recess of the sphenoid sinus, petrous apex, infratemporal fossa and petrous carotid artery, and middle and posterior skull base. 5The patient consented to the procedure.Images in the video used with permission as follows: images at 0:33 and 1:15 reused from Bozkurt et al, 3 © Georg Thieme Verlag KG; image at 0:39 from Prosser et al, 5 © John Wiley and Sons; images at 0:54, 9:03, and 9:38 from Kasemsiri et al, 1 © John Wiley and Sons; images at 1:07 and 9:44 from Falcon et al, 2 © John Wiley and Sons; image at 1:15 from Sandu et al, 4 © Springer Nature.

Microanatomic Study of the Optic Canal.

BACKGROUND: The continuous development of microsurgical techniques to treat lesions in and around the optic canal (OC) emphasizes the need for an accurate understanding of the microanatomy of the region. METHODS: Forty anatomic specimens were studied, with emphasis on the OC. The sphenoid bone and related structures were decalcified, added to animal gelatin, cut into 1-mm thick slices, and observed through a surgical microscope. The OC was considered the course that contained exclusively the optic nerve (ON) and ophthalmic artery. RESULTS: The mean distance between the medial walls of the OC was 12.2 mm, and the OC had an average length of 12.06 mm. The OC has a horizontal oval shape in the proximal (internal) segment; a round shape in the middle segment; and a vertical oval shape in the distal (external) segment at the orbital cavity. In the middle segment of the OC, the thickest wall of the OC was the lateral (average: 0.68 mm), while the medial, inferior, and superior wall measures had averages of 0.75, 0.40, and 0.39 mm, respectively. The lateral wall of the sphenoid sinus is located under the OC, and the inferior wall of the OC separates both structures. The ophthalmic artery inside the OC was always located under the ON, between the dural sheaths, and had an average diameter of 1.03 mm. CONCLUSIONS: The neurovascular structures within the OC vary in size and shape. The anatomic knowledge of the OC and its variations allows better surgical results and minimizes the surgical morbidity.

Intra- and extradural anterior clinoidectomy: anatomy review and surgical technique step by step.

PURPOSE: The complex relations of the paraclinoid area make the surgical management of the pathology of this region a challenge. The anterior clinoid process (ACP) is an anatomical landmark that hinders the visualization and manipulation of the surrounding neurovascular structures, hence in certain surgical interventions might be necessary to remove it. We reviewed the anatomical relationships that involve the paraclinoid area and detailed the step-by-step techniques of intra and extradural clinoidectomy in cadaveric specimens. MATERIALS AND METHODS: A literature review was done describing the most relevant anatomic relationships regarding the anterior clinoid process. Extradural and intradural clinoidectomy techniques were performed in six dry bone heads and in ten previously injected cadaverous specimens with colored latex (Sanan et al. in Neurosurgery 45:1267-1274, 1999) and each step of the procedure was recorded using photographic material. Finally, an analysis of the anatomical exposure achieved in each of the techniques used was performed. RESULTS: The main advantage of the intradural clinoidectomy technique is the direct visualization of the neurovascular structures adjacent to the ACP when drilling, at the same time, opening the Sylvian fissure will allow the direct visualization of the ACP variants. The main advantage offered by the extradural technique is that the dura protects adjacent eloquent structures while drilling. Among the disadvantages, it is noted that the same dura that would protect the underlying structures also prevents the direct visualization of these neurovascular structures adjacent to the ACP. CONCLUSION: We reviewed the anatomy of the paraclinoid area and made a step-by-step description of the technique of the anterior clinoidectomy in its intra- and extradural variants in cadaveric preparations for a better understanding.

Sphenoidal artery: review of the literature and analysis of a dissected arterially injected fetal orbit.

PURPOSE: The sphenoidal artery is considered a component of the complex and dangerous arterial anastomoses of the human orbitocranial region, particularly with the advent of interventional neuroimaging. The objective of this publication was to analyze the various descriptions of the sphenoidal artery in the literature as related to relevant photographs of a dissected arterially injected fetal middle cranial fossa and orbit. METHODS: Publications dealing with middle meningeal-ophthalmic arterial anastomoses, focusing on the sphenoidal artery, were reviewed. A relevant dissection of a fetal specimen was analyzed. RESULTS: The literature dealing with the sphenoidal artery is at times not in agreement. The nomenclature and anatomy of its passage through the superior orbital fissure or Hyrtl canal have variable descriptions. Photographs of the skull base of a dissected arterially injected fetal specimen show bilateral prominent orbital branches of the middle meningeal arteries. These branches entered both orbits in a course similar to the diagrammatic representations of the sphenoidal artery, and give rise to several major intraorbital arteries. This study provides the only photographic image in the literature of this variation in a human fetal anatomic dissection. CONCLUSIONS: Review of the literature dealing with the sphenoidal artery shows inconsistent nomenclature and conflicting descriptions of its anastomotic connections, and varying evolutionary and embryologic theories. Analysis of the dissected fetal skull base indicates that the sphenoidal artery is not a distinct artery but just a middle meningeal orbital arterial branch, an important component of the complex and dangerous arterial anastomoses of the human orbitocranial region.

Morphology and morphometry of the foramen venosum: a radiographic study of CBCT images and literature review.

PURPOSE: The goal of this study was to assess the morphological variations, location, and morphometric measurements of the foramen venosum (FV) and analyse its interrelationships with other foramina on cone-beam computed tomography (CBCT) scans. METHODS: A total of 269 individual CBCT scans were evaluated retrospectively. The presence or absence of FVs and their diameter, shape, and confluence to foramen ovale were recorded. The distances between anatomic structures and the FV were calculated. Appropriate statistical analysis was performed for the collected data. RESULTS: Of the 269 cases studied, nine were excluded due to duplicate foramina that made statistical analysis difficult. In the 260 evaluated scans, the FV was identified in 190 individuals (73.1%). The incidence was 148 (56.9%) on the right side and 152 (58.5%) on the left side. The FV was present unilaterally in 80 (30.8%) and bilaterally in 110 (42.3%) out of the 260 individuals. The mean maximum diameter of FV was 1.75 ± 1.27 mm, and no significant differences related to gender and age were detected (p < 0.05). The most prevalent foramen shape was the oval type (45.9% on the right side and 40.8% on the left side). CONCLUSION: FV is a very frequent anatomical variation. This foramen can exist either bilaterally or unilaterally. No significant differences related to sex, side, or age could be found in the present study. The anatomic characteristics of FV should be considered during interventions in the middle cranial fossa. CBCT imaging with lower radiation doses and thin slices may prove useful before surgical skull-base procedures.

Anatomic Nuances of the Ophthalmic Artery Origin from a Ventral Viewpoint: Considerations and Implications for Endoscopic Endonasal Surgery.

BACKGROUND: The origin of the ophthalmic artery is within the surgical field of endoscopic endonasal approaches (EEAs) to the suprasellar and parasellar regions. However, its anatomy from the endoscopic point-of-view has not been adequately elucidated. OBJECTIVE: To highlight the anatomy of the ophthalmic artery origin from an endoscopic endonasal perspective. METHODS: The origin of the ophthalmic artery was studied bilaterally under endoscopic visualization, after performing transplanum/transtubercular EEAs in 17 cadaveric specimens (34 arteries). Anatomic relationships relevant to surgery were evaluated. To complement the cadaveric findings, the ophthalmic artery origin was reviewed in 200 "normal" angiographic studies. RESULTS: On the right side, 70.6% of ophthalmic arteries emerged from the superior aspect, while 17.6% and 11.8% emerged from the superomedial and superolateral aspects of the intradural internal carotid artery, respectively. On the left, 76.5%, 17.6%, and 5.9% of ophthalmic arteries emerged from the superior, superomedial, and superolateral aspects of the internal carotid, respectively. Similar findings were observed on angiography. All ophthalmic arteries emerged at the level of the medial opticocarotid recess. Overall, 47%, 26.5%, and 26.5% of ophthalmic arteries (right and left) were inferolateral, inferior, and inferomedial to the intracranial optic nerve segment, respectively. On both sides, the intracranial length of the ophthalmic artery ranged from 1.5 to 4.5 mm (mean: 2.90 ± standard deviation of 0.74 mm). CONCLUSION: Awareness of the endoscopic nuances of the ophthalmic artery origin is paramount to minimize the risk of sight-threatening neurovascular injury during EEAs to the suprasellar and parasellar regions.

Vascular malformation of the sphenoid and temporal bone: A diagnostic dilemma.

We present a rare case of a vascular anomaly of the sphenoid and temporal bones causing an expandable mass of the temporal region with dependent patient positioning and characteristic osseous changes on imaging. Initial diagnosis considerations included multiple myeloma (MM), fibrous dysplasia (FD), Paget's disease, lymphoma, meningoencephalocele (MEC), and vascular malformation (VaM). VaMs of the head and neck are rare and typically arise in the mandible and maxilla. However, this case demonstrates a unique finding of a VaM of the sphenoid and temporal bones with important radiological features to distinguish the diagnosis of vascular anomaly from other etiologies.

Neurovascular Surgical Keys Related to Sphenoid Window: Radiologic Study of Egyptian's Sphenoid.

OBJECTIVES: The anatomic variations of the sphenoid sinus and its relation to the surrounding neurovascular structures are a subject of interest. The purpose of this study was to radiologically assess the frequency of protrusion/dehiscence of key neurovascular landmarks surrounding the Egyptians' sphenoid. METHODS: This is a cross-sectional descriptive study of sinonasal computed tomography of the sphenoid sinus in 500 adult Egyptians, conducted at Mansoura University Hospitals; Egypt, over a period of 1 year. Two archives were used for collecting the data; the hard archive and the electronic archive. Variables of interest included the extent of sphenoid sinus pneumatization; intersphenoid septation pattern; protrusion/dehiscence of the internal carotid artery, optic nerve, maxillary nerve, and vidian nerve; and detection of the Onodi cell. RESULTS: Population of this study included 265 women and 235 men. Their ages ranged from 18-68 years. The bilateral sellar-type pneumatization was shown as the most common pneumatization type (96.8%). Pneumatizations of the pterygoid process, anterior clinoid process, and greater wing of the sphenoid were identified in 9.3%, 8.9%, and 31.8% consequently. A single intersphenoid septum was detected in 85.2%, whereas multiple intersphenoid septums were noted in 11.6%. Protrusion of the internal carotid artery, optic nerve, vidian nerve, and maxillary nerve was recorded in 8.5%, 9.1%, 6.6%, and 3.4% consequently, while dehiscence was reported in 7.2%, 15%, 11.9%, and 4.2% consequently as well. Onodi cell was recognized in 18%. CONCLUSIONS: This radiologic study highlights significant variations of surgically important anatomic structures related to the sphenoid sinus in Egyptians.

The "polymorphous" history of a polymorphous skull bone: the sphenoid.

For a long time, because of its location at the skull base level, the sphenoid bone was rather mysterious as it was too difficult for anatomists to reach and to elucidate its true configuration. The configuration of the sphenoid bone led to confusion regarding its sutures with the other skull bones, its shape, its detailed anatomy, and the vascular and nervous structures that cross it. This article takes the reader on a journey through time and space, charting the evolution of anatomists' comprehension of sphenoid bone morphology from antiquity to its conception as a bone structure in the eighteenth century, and ranging from ancient Greece to modern Italy and France. The journey illustrates that many anatomists have attempted to name and to best describe the structural elements of this polymorphous bone.

Anatomy of the sphenopalatine artery and its implications for transnasal neurosurgery.

BACKGROUND: The knowledge of sinonasal vasculature is inevitable in transnasal neurosurgery. We performed an anatomical study on the sphenopalatine artery from the perspective of skull base procedures. METHODOLOGY: To analyse the anatomical landmarks of the sphenopalatine artery, arterial skull corrosion casts (26 head halves) underwent endoscopic transnasal phantom surgery. Furthermore, we performed microsurgical dissection on formaldehyde-fixated cadavers with arterial perfusion (14 head halves) as well as studied Cone Beam CT-scans of anonymised patients and cadavers (115 head sides). RESULTS: In our cadaveric material, the sphenopalatine foramen is located at the transition of the superior and middle nasal meatus (95.0%) or in the superior nasal meatus (5.0%). It is the main entry point of the branches of the sphenopalatine artery into the nasal cavity. In most cadaveric cases (25.0%), at this level there are 2 branches superiorly and 1 vessel inferiorly to the ethmoid crest. An average of 2.4 vessels leave the sphenopalatine foramen superiorly to the ethmoid crest, 97.8% of them belong to the sphenopalatine arterys posterior septal branches. An average of 2.1 branches leave the sphenopalatine foramen inferiorly to the ethmoid crest; all of them belong to the posterior lateral nasal branches. There are no cases with a single artery at the plane of the sphenopalatine foramen. We describe a triangular bony structure bordering the sphenopalatine foramen anteriorly which is built up by the palatine and ethmoid bone as well as the maxilla. According to the radiographic studies, this triangular prominence is surrounded superiorly by a posterior ethmoid cell (57.4%), the sphenoid sinus (41.7%) or the orbit (0.9%) with a varying contribution of the superior nasal meatus; inferolaterally by the maxillary sinus (98.3%) or the pterygopalatine and infratemporal fossa (1.7%) and inferomedially by the middle nasal meatus. The medial vertex of the bony triangle corresponds to the ethmoid crest of the palatine bone. In transnasal endoscopic surgery, the posterior lateral nasal branches of the sphenopalatine artery appear at the triangle's inferomedial edge, the posterior septal branches emerge at its superior edge. CONCLUSIONS: The triangular bony structure is a landmark to find and differentiate the posterior lateral nasal and posterior septal branches of the sphenopalatine artery and to identify the sphenoid sinus.

Application of 3-Dimensional Computerized Tomography Angiography for Defining Cavernous Sinus Aneurysms and Intradural Aneurysms Involving the Internal Carotid Artery Around the Anterior Clinoid Process.

OBJECTIVE: This study aimed to investigate the application of 3-dimensional computed tomography angiography (3D-CTA) for defining cavernous sinus aneurysms and intradural aneurysms involving the internal carotid artery around the anterior clinoid process. METHODS: Results from 42 patients with an aneurysm of the internal carotid artery around the anterior clinoid process who underwent 3D-CTA were reviewed and compared with those of observed clinical operations. RESULTS: Among the 42 patients, there was a total of 45 aneurysms of the internal carotid artery around the anterior clinoid process. After surgery, 33 of the 45 aneurysms were confirmed as intradural aneurysms, and the other 12 were confirmed as aneurysms in the cavernous sinus. 3D-CTA imaging of the medial sagittal plane showed that 31 out of 31 (100%) intradural aneurysms of the internal carotid artery were above the virtual line between the inferior border of the anterior clinoid process and the tuberculum sellae, and 12 out of 14 (86%) cavernous sinus aneurysms were below the virtual line (P < 0.0001). CONCLUSIONS: The virtual line between the inferior border of the anterior clinoid process and the tuberculum sellae on 3D-CTA indicates the proximal dural ring of the internal carotid artery. This line helps differentiate cavernous sinus aneurysms from intradural aneurysms involving the internal carotid artery around the anterior clinoid process.

Anatomic study of the distance between the articular eminence and foramen spinosum and foramen spinosum and petrotympanic fissure.

PURPOSE: The middle meningeal artery is in close proximity to the medial aspect of the temporomandibular joint (TMJ). A major potential complication of surgery in the area of the TMJ is possible severance of the middle meningeal artery. An understanding of the relationship of the middle meningeal artery to easily identifiable landmarks lateral to the TMJ can help prevent the complications associated with TMJ surgery. The aim of the present study was to define the location of the middle meningeal artery by relating the distance between the easily identifiable bony landmarks of the articular eminence, petrotympanic fissure, and foramen spinosum. MATERIALS AND METHODS: Using a cross-sectional study design, we selected dried skulls from the Hamman-Todd skeleton collection at the Cleveland Museum of Natural History that were older than 20 years of age at death. The primary study variables were the distances between the articular eminence and foramen spinosum and the foramen spinosum and petrotympanic fissure. To appropriately analyze the variables, stratifications of age, gender, race, and anatomic location were applied. To measure the relationship between the stratifications and distances, a multivariate analysis of variance test was performed. The statistical results were deemed significant at P < .05. RESULTS: The sample consisted of 354 skulls or a total of 708 complexes. In analyzing the data, we noted that the only stratifications that bore any statistical significance were gender, with P < .0001, and the race-distance correlation, with a P value of .0007. CONCLUSIONS: The results of the present study suggest a definite difference in regard to gender on the distance between both sets of anatomic landmarks. Future studies could be tailored to further explore the effect of age on the distance, as a slight correlation was noted in our study.

A new classification of cavernous segment of the internal carotid artery.

INTRODUCTION: The shape of the cavernous segment of the internal carotid artery (CSICA) is various in different people, which makes it difficult to be located and causes a higher possibility of injury in the transsphenoidal approach. Hence, a comprehensive study of the CSICA and a meaningful classification of it are rather helpful to the approach and other operations related to the CSICA. PURPOSE: Our study aimed to make a comprehensive measurement and classify the CSICA into different types so as to better describe its shape and position. MATERIALS AND METHODS: Computed tomographic angiography images of 146 internal carotid arteries in individuals (76 males and 70 females) ranging in age from 17 to 78 years (mean, 49.49 y) were reviewed. We measured the distances between the bilateral CSICA at 5 positions in the coronal plane and the angle of the posterior curve segment in the sagittal plane. According to these statistics, we divided the CSICA into different types. RESULTS: The distance between the medial walls of the bilateral internal carotid artery is similar to the previous relevant study. We classified the horizontal segment of the CSICA into 5 types: types 1, 2, 3, 4, and 5. Among the individuals we measured, the proportion of each type is 8.2%, 25.3%, 39.7%, 19.9%, and 6.9%. In addition, the posterior curve segment of the CSICA can be classified into 4 types: types Z, A, S, and O. Among the 292 sides we measured, the proportion of each type is 22.6%, 17.8%, 21.9%, and 37.7%. Furthermore, 80.8% of the people with bilateral sides of type O belonged to type 3 and 72.7% of the people with bilateral sides of type Z belonged to type 2. CONCLUSIONS: The detailed classification of the CSICA is helpful to understand its complexity. The classification of the CSICA can guide the surgeons in the transsphenoidal approach to avoid injuring and to simplify the location of the whole CSICA.

The anatomical relations of the sphenoid sinus and their implications in sphenoid endoscopic surgery.

Alongside the past development of endoscopic sinus surgery, knowledge about the anatomy of the sinuses has become crucial for surgeons. The sphenoid sinus is one of the most variable of all sinuses. Its relations to vital vascular and nervous elements make its approach a challenge for endoscopic surgeons. These relations include the internal carotid artery, the optic nerve, the pituitary gland, the Vidian nerve, and other vascular and nervous elements depending on the size of the sinus. This paper will make a review of these anatomical relations and their importance in endoscopic sphenoid surgery.

The Dorello canal: historical development, controversies in microsurgical anatomy, and clinical implications.

Interest in studying the anatomy of the abducent nerve arose from early clinical experience with abducent palsy seen in middle ear infection. Primo Dorello, an Italian anatomist working in Rome in the early 1900s, studied the anatomy of the petroclival region to formulate his own explanation of this pathological entity. His work led to his being credited with the discovery of the canal that bears his name, although this structure had been described 50 years previously by Wenzel Leopold Gruber. Renewed interest in the anatomy of this region arose due to advances in surgical approaches to tumors of the petroclival region and the need to explain the abducent palsies seen in trauma, intracranial hypotension, and aneurysms. The advent of the surgical microscope has allowed more detailed anatomical studies, and numerous articles have been published in the last 2 decades. The current article highlights the historical development of the study of the Dorello canal. A review of the anatomical studies of this structure is provided, followed by a brief overview of clinical considerations.

Recurrent infarction of sphenoid bone with subperiosteal collection in a child with sickle cell disease.

Infarction of the orbital bone in patients with sickle cell disease is very rare. The authors report a young boy who presented twice with marked acute proptosis and eyelid swelling of the right eye resulting from infarction in the greater wing of the sphenoid bone accompanied by an orbital subperiosteal collection. The time interval between the 2 attacks was 3 years.

Maxillary sinus vascularization: a cadaveric study.

The goal of this study was the investigation of the arterial blood supply to the maxillary sinus to give clinicians the basis for a better understanding of the origin of vascular complications that can derive from surgical procedures at this level. The study consisted of 30 sinuses from 15 human cadavers with an age range of 59 to 90 years. To define the complex vascularization of the maxillary sinus, the afferent vascular network was injected with liquid latex mixed with red india ink through the external carotid arteries. An intraosseous anastomosis between the dental branch of the posterior superior alveolar artery, also known as alveolar antral artery, and the infraorbital artery was found in 100% of cases. Such an anastomosis seemed to guarantee the blood supply to the sinus membrane, to the periosteal tissues, and especially to the anterior lateral wall of the sinus. Moreover, the gingival branch of the posterior superior alveolar artery was found to anastomose an extraosseous branch of the infraorbital artery in 10 sinuses. The examination of the maxillary sinus also showed a close anatomic relationship among the sinus posterior wall, the descending palatine artery, and the sphenopalatine artery in all 30 sinuses. Small branches deriving from the posterior lateral nasal arteries have been found to perforate the nasal wall laterally and reach the mucosa of the maxillary sinus. A sound knowledge of the maxillary sinus vascularization is essential to prevent vascular complications during surgical operations involving this region.